Marine peptides and their anti-infective activities

Abstract

Marine bioresources are a valuable source of bioactive compounds with industrial and nutraceutical potential. Numerous clinical trials evaluating novel chemotherapeutic agents derived from marine sources have revealed novel mechanisms of action. Recently, marine-derived bioactive peptides have attracted attention owing to their numerous beneficial effects. Moreover, several studies have reported that marine peptides exhibit various anti-infective activities, such as antimicrobial, antifungal, antimalarial, antiprotozoal, anti-tuberculosis, and antiviral activities. In the last several decades, studies of marine plants, animals, and microbes have revealed tremendous number of structurally diverse and bioactive secondary metabolites. However, the treatments available for many infectious diseases caused by bacteria, fungi, and viruses are limited. Thus, the identification of novel antimicrobial peptides should be continued, and all possible strategies should be explored. In this review, we will present the structures and anti-infective activity of peptides isolated from marine sources (sponges, algae, bacteria, fungi and fish) from 2006 to the present.

Figure 1

Amino acid sequence of aurelin (1). Aurelin was isolated from the mesoglea of a scyphoid jellyfish, Aurelia aurita [31]. Aurelin has six cysteine residues, forming three disulfide bonds.

Figure 2

Amino acid sequence of arenicin-1 (2). Arenicin was isolated from the marine polychaete Arenicola marina [32]. Arenicin-1 contained one disulfide bond and formed a typical β-hairpin structure.

Figure 3

Sequence alignment of three tilapia hepcidins (TH1-5, TH2-2, and TH2-3). Three hepcidins (4) were isolated from tilapia (Oreochromis mossambicus) [35]. Identical or similar amino acid residues are in same colors. Gaps are inserted to obtain maximum homology.

Figure 4

Amino acid sequence of scygonadin (5). Scygonadin was isolated from the seminal plasma of the mud crab, Scylla serrate [36,37]. Scygonadin contained α-helices and had 39 residues on the same hydrophobic surface. Scygonadin may interact with cell membranes.

Figure 5

The alignment of centrocin 1 (10) and 2 (11) from Strongylocentrotus droebachiensis (A) and the proposed structure of centrocins 1a and 2 (B) [42]. The predicted cleavage site between the signal peptides and the prosequences are shown by a solid triangle (▼). Identical residues are shaded in black, whereas similar residues are shaded in gray. The boxes indicate the heavy chain and the light chain regions. In the proposed structure of centrocin, the heavy chain and the light chain are connected by disulfide bridges. The brominated tryptophan in position 2 of the active centrocin is labeled with a Br on the top.

Figure 6

Helical wheel diagrams of halocyntin (A, 12) and residues 2-19 of papillosin (B, 13) are shown, with the polar residues shaded gray. The clearly evident clustering of polar and apolar residues imparts amphipathicity [43].

Figure 7

Amino acid sequences and overall peptide structure of hyastatin (14), isolated from the hemocytes of Hyas araneus [44]. The different regions are distinguished with boxes and given a designation below. The sequence of hyastatin has been submitted to the NCBI GenBank database with the accession number FJ764995.

Figure 8

Deduced amino acid sequences of preprodamicornin. The arrow identifies the cleavage site of the signal peptide. The dibasic cleavage site between the acidic N-terminal proregion and the cationic C-terminal region is outlined in black. The damicornin active peptide is underlined in black. The cysteine residues and glycine amidation signal are shown in bold [51].

Figure 9

Structure of Cadiolides (29–32). Caldiolides were isolated from the tunicate Pseudodistoma antinboja by activity-guided fractionations [53].

Figure 10

Structure of cytosporomes B (33) and E (34). Cytosporomes were isolated a strain of the endophytic fungus Leucostoma persoonii [54].

Figure 11

Structure of Anthracimycin (35). Anthracimycin were isolated from the Steptomyces bacteria [55].

Figure 12

Amino acid sequence of halocidin (36). Halocidin were identified from the hemocytes of Hyas araneus [56]. Vertical bars in the sequence indicate a disulfide bond between two cysteine residues. The asterisk (*) denotes C-terminal amidation.

Figure 13

Structure of C(15)-surfactin (44). Surfactin was isolated from Bacillus amyloliquefaciens [101].

Figure 14

Structure of albopunctatone (63). Albopunctatone was isolated ascidian Didemnum albopunctatum [76].

Figure 15

Structure of diketopiperazines (70–81) [80].

Figure 16

Structure of Homophymines A–E (99–103) and A1–E1 (104–108). Homophymines are a series of cyclodepsipeptides isolated from Homophymia sp. collected from shallow waters off the east coast of New Caledonia [87,88].